A New Calibration of Star Formation Rate in Galaxies Based on Polycyclic Aromatic Hydrocarbon Emission

• Published in: The Astrophysical journal Vol. 884; no. 2; pp. 136 - 145
• Main Authors: Xie, Yanxia, Ho, Luis C.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 20-10-2019; IOP Publishing
• Subjects: Aromatic hydrocarbons; Astrophysics; Calibration; dust, extinction; Dwarf galaxies; Emission; Galactic evolution; galaxies: dwarf; galaxies: formation; galaxies: starburst; Hydrocarbons; Infrared spectra; Luminosity; Massive stars; Ozone; Photodissociation; Polycyclic aromatic hydrocarbons; Star & galaxy formation; Star formation; Star formation rate; Stars & galaxies; Stellar mass
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab4200

Polycyclic aromatic hydrocarbon (PAH) emission has long been proposed to be a potential star formation rate indicator, as it arises from the photodissociation region bordering the Strömgren sphere of young, massive stars. We apply a recently developed technique of mid-infrared spectral decomposition to obtain a uniform set of PAH measurements from Spitzer low-resolution spectra of a large sample of star-forming galaxies spanning a wide range in stellar mass (M 106-1011.4 M ) and star formation rate (∼0.1-2000 M yr−1). High-resolution spectra are also analyzed to measure [Ne ii] 12.8 m and [Ne iii] 15.6 m, which effectively trace the Lyman continuum. We present a new relation between PAH luminosity and star formation rate based on the [Ne ii] and [Ne iii] lines. Calibrations are given for the integrated 5-15 m PAH emission, the individual features at 6.2, 7.7, 8.6, and 11.3 m, as well as several mid-infrared bandpasses sensitive to PAH. We confirm that PAH emission is suppressed in low-mass dwarf galaxies, and we discuss the possible physical origin of this effect.